Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$215.37	7.194%	$230.8637	$230.86	$230.85	$230.90
Purchase #2	$49.62	11.588%	$55.37	$55.37	$55.35	$55.40
Purchase #3	$78.82	10.262%	$86.9085	$86.91	$86.90	$86.90
Purchase #4	$134.31	11.855%	$150.2325	$150.23	$150.25	$150.20
Purchase #5	$56.78	7.703%	$61.1538	$61.15	$61.15	$61.20
Purchase #6	$48.85	11.266%	$54.3534	$54.35	$54.35	$54.40
Purchase #7	$212.49	4.256%	$221.5336	$221.53	$221.55	$221.50
7 purchase totals =	$796.24		$860.4155	$860.40	$860.40	$860.50